One of the issues with people grasping the idea that iterative approaches work best seems to be that most people are educated to believe that they can perfectly plan then perfectly execute. With this mental model, it is extremely difficult to get the idea of iterative approaches to stick. Perhaps this quick Ted Video from Tom Wujec will help. He summarizes his marshmallow experiments and shows how kindergartners beat MBAs because of their iterative approaches…take a look!